This disclosure generally relates to systems and methods for repairing structures comprised of composite materials, and in particular, to methods and systems that use double vacuum debulking to repair structural components made of composite material, such as carbon fiber/epoxy composite material.
The use of structures comprised of composite materials has grown in popularity, particularly in such applications as aircraft airframes, where benefits include increased strength and rigidity, reduced weight and reduced parts count. When damaged, however, composite structures often require extensive repair work.
It is known to provide a repair method and system that uses double vacuum debulking (DVD) to repair a composite structure. As used herein, the term “double vacuum debulking” means a process in which a stack of repair plies is subjected to vacuum and mild heating without being compacted by atmospheric pressure. The purpose of the double vacuum debulk process is to minimize porosity in the repair plies by drawing air and other gases from between the plies while they are in an uncompacted state.
One known DVD process for repairing graphite/epoxy primary and secondary structures requires extensive preparation and multiple process steps to perform acceptable composite repairs. The steps required for processing successful composite repairs are very time consuming and labor intensive. For example, one existing solution requires the composite repair patch to be processed in an off-aircraft chamber to perform debulking (i.e., forming, degassing, consolidating, and staging the repair patch) for subsequent application onto the structure being repaired. More specifically, this DVD composite repair system is an off-aircraft process using support tooling (i.e., a vacuum chamber) to provide the first stage of producing a degassed, consolidated composite repair for application onto parent structure. The repairs in this process are produced on either flat or contoured support tooling, and consolidated using the first stage of the DVD process. The processed repair patch is then transferred to the parent aircraft structure and is cured in a second stage process using an adhesive layer in the bondline interface. Flat repair patches can be fabricated and applied to contoured structure, but when the contour becomes complex or radical, then separate contour matched tooling is required to fabricate the repair patch.
A manufacturer of aircraft made from composite materials may elect to transport a double vacuum debulk tool of the above-described type around the world to support aircraft repairs. However, current double vacuum debulk tools are heavy. Most examples found are box-shaped vacuum chambers. One known example has a convex dome. The bottom of the chamber is a base plate that the repair patch rests on. These tools are difficult to move and expensive to transport.
The design of a double vacuum debulk tool that is lighter in weight could save transportation costs and provide other advantages.